Most entries, but not all. Disturbingly, all of the worst entries I have ever read have been in the sciences. Wander off the big ideas in the sciences, and you’re likely to run into entries that are excessively technical and provide almost no context, making them effectively incomprehensible.
This failure is a minor problem for Wikipedia, as most of the entries people rely on are fine. But I’d argue that it’s a significant problem for science. The problematic entries reinforce the popular impression that science is impossible to understand and isn’t for most people—they make science seem elitist. And that’s an impression that we as a society really can’t afford.
From Editorial: Wikipedia fails as an encyclopedia, to science’s detriment | Ars Technica